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1.
Nanoscale Adv ; 6(8): 2149-2165, 2024 Apr 16.
Article in English | MEDLINE | ID: mdl-38633039

ABSTRACT

The rapid growth, integration, and miniaturization of electronics have raised significant concerns about how to handle issues with electromagnetic interference (EMI), which has increased demand for the creation of EMI shielding materials. In order to effectively shield against electromagnetic interference (EMI), this study developed a variety of thermoplastic polyurethane (TPU)-based nanocomposites in conjunction with CoFe2O4 nanoparticles and graphite. The filler percentage and nanocomposite thickness were tuned and optimized. The designed GF15-TPU nanocomposite, which has a 5 mm thickness, 15 weight percent cobalt ferrite nanoparticles, and 35 weight percent graphite, showed the highest total EMI shielding effectiveness value of 41.5 dB in the 8.2-12.4 GHz frequency range, or 99.993% shielding efficiency, out of all the prepared polymer nanocomposites. According to experimental findings, the nanocomposite's dipole polarization, interfacial polarization, conduction loss, eddy current loss, natural resonance, exchange resonance, multiple scattering, and high attenuation significantly contribute to improving its electromagnetic interference shielding properties. The created TPU-based nanocomposites containing graphite and CoFe2O4 nanoparticles have the potential to be used in communication systems, defense, spacecraft, and aircraft as EMI shielding materials.

2.
Adv Colloid Interface Sci ; 326: 103137, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38555833

ABSTRACT

The electromagnetic interference shielding and microwave attenuation capabilities of ZnO semiconductor nanocomposites have recently been improved using a variety of approaches by correctly modifying their permittivity. To improve microwave attenuation, ZnO semiconductor nanostructures have been combined with graphene, multi-wall carbon nanotubes, metal nanoparticles and their alloys, two-dimensional MXene, spinel ferrite magnetic nanoparticles, polymer systems, and textiles. This paper covers the opportunities and constraints that these cutting-edge nanocomposites in the field of electromagnetic wave absorption encounter as well as the research progress of ZnO semiconductor-based nanocomposite. The structure-function relationship of electromagnetic wave absorption nanocomposites, design strategies, synthesis techniques, and various types of advanced nanocomposites based on ZnO semiconductor are also covered. In order to design and prepare high efficiency ZnO semiconductor based electromagnetic wave absorbing materials for use in applications of next-generation electronics and aerospace, this article can offer some useful ideas.

3.
Polymers (Basel) ; 16(3)2024 Jan 23.
Article in English | MEDLINE | ID: mdl-38337198

ABSTRACT

A styrene-butadiene-styrene co-polymer matrix nanocomposite filled with graphene nanoplatelets was studied to prepare chemiresistive volatile organic compounds (VOCs) room temperature sensors with considerable response and selectivity. Nanofiller concentration was estimated from the electrical conductivity percolation behaviour of the nanocomposite. Fabricated sensors provided selective relative responses to representative VOCs differing by orders of magnitude. Maximum observed average relative responses upon exposure to saturated vapours of the tested VOCs were ca. 23% for ethanol, 1600% for acetone, and the giant values were 9 × 106% for n-heptane and 10 × 106% for toluene. The insensitivity of the sensor to the direct saturated water vapour exposure was verified. Although high humidity decreases the sensor's response, it paradoxically enhances the resolution between hydrocarbons and polar organics. The non-trivial sensing mechanism is explained using the Hansen solubility parameters (HSP), enabling a rational design of new sensors; thus, the HSP-based class of sensors is outlined.

4.
Carbohydr Polym ; 327: 121640, 2024 Mar 01.
Article in English | MEDLINE | ID: mdl-38171669

ABSTRACT

In this work, conductive composite hydrogels with covalently attached polypyrrole (PPy) nanoparticles are prepared. Hydrogels are based on partially re-acetylated chitosan soluble at physiological pH without any artificial structural modifications or need for an acidic environment, which simplifies synthesis and purification. Low-toxic and sustainable dialdehyde cellulose (DAC) was used for crosslinking chitosan and covalent anchoring of PPy colloidal particles. The condensation reaction between DAC and PPy is reported for the first time and improves not only the anchoring of PPy particles but also control over the properties of the final composite. The soluble chitosan and PPy particles are shown to act in synergy, which improves the biological properties of the materials. Prepared composite hydrogels are non-cytotoxic, non-irritating, antibacterial, can capture reactive oxygen species often related to excessive inflammation, have conductivity similar to human tissues, enhance in vitro cell growth (migration assay), and have immunomodulatory effects related to the stimulation of neutrophils and macrophages. The covalent attachment of PPy also strengthens the hydrogel network. The aldol condensation as a method for PPy covalent anchoring thus presents an interesting possibility for the development of advanced biomaterials in the future.


Subject(s)
Chitosan , Humans , Chitosan/chemistry , Polymers/chemistry , Hydrogels/pharmacology , Hydrogels/chemistry , Pyrroles/chemistry , Antioxidants/pharmacology , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/chemistry , Anti-Inflammatory Agents/pharmacology
5.
ACS Catal ; 13(19): 12970-12982, 2023 Oct 06.
Article in English | MEDLINE | ID: mdl-37822857

ABSTRACT

In this work, we demonstrate that amorphous and porous molybdenum silicate microspheres are highly active catalysts for heterogeneous propylene metathesis. Homogeneous molybdenum silicate microspheres and aluminum-doped molybdenum silicate microspheres were synthesized via a nonaqueous condensation of a hybrid molybdenum biphenyldicarboxylate-based precursor solution with (3-aminopropyl)triethoxysilane. The as-prepared hybrid metallosilicate products were calcined at 500 °C to obtain amorphous and porous molybdenum silicate and aluminum-doped molybdenum silicate microspheres with highly dispersed molybdate species inserted into the silicate matrix. These catalysts contain mainly highly dispersed MoOx species, which possess high catalytic activity in heterogeneous propylene metathesis to ethylene and butene. Compared to conventional silica-supported MoOx catalysts prepared via incipient wetness impregnation (MoIWI), the microspheres with low Mo content (1.5-3.6 wt %) exhibited nearly 2 orders of magnitude higher steady-state propylene metathesis rates at 200 °C, approaching site time yields of 0.11 s-1.

6.
Nanoscale Adv ; 5(11): 3091-3103, 2023 May 30.
Article in English | MEDLINE | ID: mdl-37260485

ABSTRACT

The impact of geometric features, light absorption spectra, and electrochemical active surface area on photoelectrochemical properties was investigated in this work. Nanoforests of ZnO nanorods with rationally controlled morphologies were grown on ITO substrates by the hydrothermal method and utilized as a model for this purpose. The size of the nanorods was systematically adjusted by varying the concentration of polyethyleneimine as a cation surfactant in the growth solution. It was found that the emergent geometric characteristics (i.e. the aspect ratio) increased almost at the same pace as the electrochemically active surface area, but the light scattering effect slightly increased as a result of the random spatial orientation of the nanorods. The large surface area and the void space between nanorods increased the photon-to-current conversion efficiency by promoting the hole transfer process at the electrode/electrolyte interface. A maximum photocurrent density of 0.06 mA cm-2 (0.5 V vs. NHE) for smaller diameter and length ZnO nanorods (ZnO-P1) was obtained under 365 nm UV light illumination. Additionally, we provide visual evidence that a shorter photogenerated hole diffusion distance results in improved charge separation efficiency using Mn2+ as the photogenerated hole imaging agent. Therefore, the present work demonstrates a facile strategy for nanoforest morphology improvement for generating strong contact at the ZnO NR electrode/electrolyte interface, which is favourable in energy conversion and storage technologies.

7.
Pharmaceuticals (Basel) ; 16(4)2023 Mar 28.
Article in English | MEDLINE | ID: mdl-37111260

ABSTRACT

A new solution for local anesthetic and antibiotic delivery after eye surgery is presented. A contact lens-shaped collagen drug carrier was created and loaded by Levofloxacin and Tetracaine with a riboflavin crosslinked surface layer, thus impeding diffusion. The crosslinking was confirmed by Raman spectroscopy, whereas the drug release was investigated using UV-Vis spectrometry. Due to the surface barrier, the drug gradually releases into the corneal tissue. To test the function of the carrier, a 3D printed device and a new test method for a controlled drug release, which mimics the geometry and physiological lacrimation rate of the human eye, were developed. The experimental setup with simple geometry revealed that the prepared drug delivery device can provide the prolonged release profile of the pseudo-first-order for up to 72 h. The efficiency of the drug delivery was further demonstrated using a dead porcine cornea as a drug recipient, without the need to use live animals for testing. Our drug delivery system significantly surpasses the efficiency of antibiotic and anesthetic eyedrops that would have to be applied approximately 30 times per hour to achieve the same dose as that delivered continuously by our device.

8.
Polymers (Basel) ; 15(7)2023 Mar 24.
Article in English | MEDLINE | ID: mdl-37050233

ABSTRACT

A wearable and stretchable strain sensor with a gauge factor above 23 was prepared using a simple and effective technique. Conducting nanocomposite strands were prepared from styrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer (SEBS) and carbon black (CB) through a solvent-processing method that uses a syringe pump. This novel nanocomposite preparation technique is a straightforward and cost-effective process and is reported in the literature for the first time. The work included two stages: the flexible nanocomposite preparation stage and the piezoresistive sensor stage. Depending on its molecular structure, the thermoelastic polymer SEBS is highly resilient to stress and strain. The main aim of this work is to fabricate a highly flexible and piezoresistive nanocomposite fibre/strand. Among the prepared composites, a composite corresponding to a composition just above the percolation threshold was selected to prepare the strain sensor, which exhibited good flexibility and conductivity and a large piezoresistive effect that was linearly dependent on the applied strain. The prepared nanocomposite sensor was stitched onto a sports T-shirt. Commercially available knee and elbow sleeves were also purchased, and the nanocomposite SEBS/CB strands were sewn separately on the two sleeves. The results showed a high sensitivity of the sensing element in the case of breathing activity (normal breathing, a 35% change, and deep breathing at 135%, respectively). In the case of knee and elbow movements, simultaneous measurements were performed and found that the sensor was able to detect movement cycles during walking.

9.
Micromachines (Basel) ; 14(3)2023 Mar 12.
Article in English | MEDLINE | ID: mdl-36985051

ABSTRACT

The present work investigates the NO2 sensing properties of acceptor-doped ferrite perovskite nanostructures. The Sr-doped BiFeO3 nanostructures were synthesized by a salt precursor-based modified pechini method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The synthesized materials were drop coated to fabricate chemoresistive gas sensors, delivering a maximum sensitivity of 5.2 towards 2 ppm NO2 at 260 °C. The recorded values of response and recovery time are 95 s and 280 s, respectively. The sensor based on Bi0.8Sr0.2FeO3-δ (BSFO) that was operated was shown to have a LOD (limit of detection) as low as 200 ppb. The sensor proved to be promising for repeatability and selectivity measurements, indicating that the Sr doping Bismuth ferrite could be a potentially competitive material for sensing applications. A relevant gas-sensing mechanism is also proposed based on the surface adsorption and reaction behavior of the material.

10.
Int J Mol Sci ; 23(15)2022 Aug 08.
Article in English | MEDLINE | ID: mdl-35955965

ABSTRACT

New anti-octadecaborane(22) laser dyes have been recently introduced. However, their application in solid thin films is limited, despite being very desirable for electronics. Spectroscopic methods, photoluminescence (PL), and infrared reflection-absorption spectroscopy (IRRAS), are here used to reveal structural responses to a temperature change in thin polymer films made of π- and σ-conjugated and non-conjugated polymers and anti-octadecaborane(22) and its tetra-alkylatedderivatives. It has been observed that borane clusters are not firmly fixed within polymer matrices and that their ability for diffusion out of the polymer film is unprecedented, especially at higher temperatures. This ability is related to thermodynamic transitions of polymer macromolecular chains. PL and IRRAS spectra have revealed a clear correlation with ß-transition and α-transition of polymers. The influence of structure and molecular weight of a polymer and the concentration and the substitution type of clusters on mobility of borane clusters within the polymer matrix is demonstrated. A solution is proposed that led to an improvement of the temperature stability of films by 45 °C. The well-known spectroscopic methods have proved to be powerful tools for a non-routine description of the temperature behavior of both borane clusters and polymer matrices.


Subject(s)
Boranes , Polymers , Coloring Agents , Lasers , Polymers/chemistry , Spectrophotometry, Infrared , Temperature
11.
RSC Adv ; 12(25): 16277-16290, 2022 May 23.
Article in English | MEDLINE | ID: mdl-35733696

ABSTRACT

Synthesis of casein-derived carbon nanodots (CND) using a microwave-assisted approach, giving a high product yield (25%), is reported. Casein was used as a sustainable carbon source, and polyvinylpyrrolidone was used as a stabilizer for the nanodots. The size of the prepared amorphous CND corresponds to individual casein coils, which were only partially carbonized. They were obtained due to the disintegration of casein micelles and submicelles within the microwave-assisted solvothermal process. The resulting nanodots had bright photoluminescence, and their electronic structure and optical properties were investigated. A novel competitive model of their luminescence mechanism was introduced to explain a phenomenon beyond the standard models. The synthesized carbon nanodots were used as luminescent ink for anticounterfeit applications. A polymer matrix nanocomposite was prepared by dispersing the nanodots in a flexible and robust poly(styrene-ethylene-butylene-styrene) tri-block copolymer (SEBS) using the solution cast method. For the first time, the effect of CND on the luminescence and mechanical properties of the SEBS/CND self-supporting films was studied. The film was also studied as a phosphor for light-emitting diodes, with a unique experimental setup to avoid self-absorption, which results in low efficiency and eliminates the excess UV transmitted. Because of their high luminescence, photostability, and mechanical properties, these CND could be used as luminescent labels in the packaging and optoelectronics industries.

12.
Carbohydr Polym ; 292: 119661, 2022 Sep 15.
Article in English | MEDLINE | ID: mdl-35725164

ABSTRACT

Sequential periodate-chlorite oxidation of sodium hyaluronate to 2,3-dicarboxylated hyaluronate (DCH), a novel biocompatible and highly functionalized derivative bearing additional pair of COOH groups at C2 and C3 carbons of oxidized ᴅ-glucuronic acid units, is investigated. The impact of various reaction parameters (time, oxidizer concentration, and molar amount) on DCH's composition, molecular weight, degree of oxidation, and cytotoxicity are investigated to guide the synthesis of DCH derivatives of desired properties. Subsequently, fully (99%) and partially (70%) oxidized DCH derivatives were compared to untreated sodium hyaluronate in terms of anticancer drug cisplatin loading efficacy, carrier capacity, drug release rates, and cytotoxicity towards healthy and cancerous cell lines. DCH derivatives were found to be superior in every aspect, having nearly twice the carrier capacity, significantly slower release rates, and higher efficacy. DCH is thus a highly interesting hyaluronate derivative with an adjustable degree of oxidation, molecular weight, and great potential for further modifications.


Subject(s)
Glycosaminoglycans , Hyaluronic Acid , Drug Liberation , Molecular Weight , Oxidation-Reduction
13.
Int J Mol Sci ; 23(5)2022 Feb 26.
Article in English | MEDLINE | ID: mdl-35269754

ABSTRACT

CuxCo1-xFe2O4 (x = 0.33, 0.67, 1)-reduced graphene oxide (rGO)-thermoplastic polyurethane (TPU) nanocomposites exhibiting highly efficient electromagnetic interference (EMI) shielding were prepared by a melt-mixing approach using a microcompounder. Spinel ferrite Cu0.33Co0.67Fe2O4 (CuCoF1), Cu0.67Co0.33Fe2O4 (CuCoF2) and CuFe2O4 (CuF3) nanoparticles were synthesized using the sonochemical method. The CuCoF1 and CuCoF2 exhibited typical ferromagnetic features, whereas CuF3 displayed superparamagnetic characteristics. The maximum value of EMI total shielding effectiveness (SET) was noticed to be 42.9 dB, 46.2 dB, and 58.8 dB for CuCoF1-rGO-TPU, CuCoF2-rGO-TPU, and CuF3-rGO-TPU nanocomposites, respectively, at a thickness of 1 mm. The highly efficient EMI shielding performance was attributed to the good impedance matching, conductive, dielectric, and magnetic loss. The demonstrated nanocomposites are promising candidates for a lightweight, flexible, and highly efficient EMI shielding material.


Subject(s)
Nanocomposites , Nanoparticles , Aluminum Oxide , Ferric Compounds , Graphite , Magnesium Oxide , Polyurethanes
14.
Int J Biol Macromol ; 206: 927-938, 2022 May 01.
Article in English | MEDLINE | ID: mdl-35292283

ABSTRACT

Properties and applications of gold nanoparticles (AuNPs) depend on their characteristics which are intrinsically connected to the reducing and capping agents used in their synthesis. Although polysaccharides are commonly used for Au salt reduction, the control over the result is often limited. Here, the selectively dicarboxylated cellulose (DCC) and hyaluronate (DCH) with adjustable composition and molecular weight are used for the first time as reducing and capping agents for AuNPs preparation in an environmental friendly one-step synthesis. Mechanism of reduction and structure-function relationships between the composition of oxidized polysaccharides and properties of formed AuNPs are elucidated and the variances in the macromolecular architecture of dicarboxypolysaccharides are applied to guide the growth of AuNPs. While the homogenous structure and high density of carboxyl groups of fully-oxidized DCC induced isotropic growth of small and uniform AuNPs with good catalytic performance (d = ~20 nm, TOF = 7.3 min-1, k = 1.47 min-1), the lower stabilizing potential and slower reduction rates of the DCH induced the anisotropic growth of larger polyhedral ~50 nm nanoparticles, which increased the Surface-Enhanced Raman Scattering efficacy (9× stronger Raman signals on average compared to AuDCC). The use of dicarboxypolysaccharides with adjustable composition and properties thus introduced a new degree of freedom for the preparation of AuNPs with desired properties.


Subject(s)
Gold , Metal Nanoparticles , Catalysis , Cellulose/chemistry , Gold/chemistry , Metal Nanoparticles/chemistry , Spectrum Analysis, Raman
15.
Polymers (Basel) ; 14(3)2022 Feb 08.
Article in English | MEDLINE | ID: mdl-35160630

ABSTRACT

Electronic devices based on polymer thin films have experienced a tremendous increase in their efficiency in the last two decades. One of the critical factors that affects the efficiency of polymer solar cells or light emitting devices is the presence of structural defects that controls non-radiative recombination. The purpose of this report is to demonstrate a non-trivial thickness dependence of optoelectronic properties and structure (dis)order in thin conductive poly(9,9-dioctyfluorene-alt-benzothiadiazole), F8BT, polymer films. The UV-Vis absorption spectra exhibited blue shift and peak broadening; significant changes in 0-0 and 0-1 radiative transition intensity was found in photoluminescence emission spectra. The density of state (DOS) was directly mapped by energy resolved-electrochemical impedance spectroscopy (ER-EIS). Satellite states 0.5 eV below the lowest unoccupied molecular orbital (LUMO) band were revealed for the thinner polymer films. Moreover, the decreasing of the deep states density in the band gap manifested an increment in the material structural ordering with increasing thickness. Changes in the ratio between crystalline phases with face-on and edge-on orientation of F8BT chains were identified in the films by grazing-incidence wide angle X-ray scattering technique. A thickness threshold in all investigated aspects of the films at a thickness of about 100 nm was observed that can be attributed to the development of J-H aggregation in the film structure and mutual interplay between these two modes. Although a specific structure-property relationship thickness threshold value may be expected for thin films prepared from various polymers, solvents and under different process conditions, the value of about 100 nm can be generally considered as the characteristic length scale of this phenomenon.

16.
Carbohydr Polym ; 279: 119022, 2022 Mar 01.
Article in English | MEDLINE | ID: mdl-34980346

ABSTRACT

A little is known about the link between the macromolecular architecture of dialdehyde polysaccharides (DAPs), their crosslinking capabilities, and the properties of resulting hydrogels. Here, DAPs based on cellulose, dextrin, dextran, and hyaluronate were compared as crosslinkers for poly(vinyl alcohol), PVA. The swelling, network parameters, viscoelastic properties, porosity, and cytotoxicity of PVA/DAP hydrogels were investigated concerning the crosslinker structure, molecular weight, aldehyde group density per macromolecule, and the size of spontaneously formed crosslinker nano-assemblies. Generally, crosslinkers based on linear polysaccharides (cellulose, hyaluronate) performed more reliably, while the presence of branching could be both beneficial (dextran) but also detrimental (dextrin) at lower crosslinker concentrations. For example, the hydrogel swelling differed by up to one-third (600 vs. 400%) and storage modulus even by up to one half (~7000 vs. ~3500 Pa) depending on crosslinker structure and properties. These differences were rationalized by variances in crosslinking modes derived based on obtained data.


Subject(s)
Cross-Linking Reagents/chemistry , Hydrogels/chemistry , Polysaccharides/chemistry , Polyvinyl Alcohol/chemistry , Animals , Cell Survival/drug effects , Cross-Linking Reagents/pharmacology , Hydrogels/pharmacology , Mice , NIH 3T3 Cells , Polysaccharides/pharmacology , Polyvinyl Alcohol/pharmacology
17.
Int J Mol Sci ; 24(1)2022 Dec 27.
Article in English | MEDLINE | ID: mdl-36613884

ABSTRACT

Band bending modification of metal/semiconductor hybrid nanostructures requires low-cost and effective designs in photoelectrochemical (PEC) water splitting. To this end, it is evinced that gradient doping of Au nanoparticles (NPs) inwards the ZnO nanorods (NRs) through thermal treatment facilitated faster transport of the photo-induced charge carriers. Systematic PEC measurements show that the resulting gradient Au-doped ZnO NRs yielded a photocurrent density of 0.009 mA/cm2 at 1.1 V (vs. NHE), which is 2.5-fold and 8-fold improved compared to those of Au-sensitized ZnO and the as-prepared ZnO NRs, respectively. The IPCE and ABPE efficiency tests confirmed the boosted photoresponse of gradient Au-incorporated ZnO NRs, particularly in the visible spectrum due to the synergistic surface plasmonic effect of Au NPs. A gradient Au dopant profile promoted the separation and transfer of the photo-induced charge carriers at the electrolyte interface via more upward band bending according to the elaborated electrochemical impedance spectroscopy and Kelvin probe force microscopy analyses. Therefore, this research presents an economical and facile strategy for preparing gradient plasmonic noble NP-incorporated semiconductor NRs, which have excellent potential in energy conversion and storage technologies.


Subject(s)
Metal Nanoparticles , Nanostructures , Nanotubes , Zinc Oxide , Gold
18.
Nanomaterials (Basel) ; 13(1)2022 Dec 21.
Article in English | MEDLINE | ID: mdl-36615930

ABSTRACT

The concentration of nanoparticles in the ambient air can lead to induced toxicities; however, it appears that nanoparticles' unique properties are completely omitted when assessing health risks. This paper aims to enhance the EPA health risk assessment by incorporating two new variables that consider the size of nanoparticles: the toxicity multiplier and the size multiplier. The former considers the qualitative aspect of the size of particles within a concentration, whilst the latter takes into account the effects associated with the number of particles of the specific i-th size distribution interval. To observe the impact of the new variables, a case study was performed. The studied element was cadmium, which was measured using ICP-MS to discover concentrations of size fractions, ranging from <15.1 to <9830 nm. Next, the cadmium concentration is assessed using both the current state-of-the-art method and the proposed method with adjustments. Based on the new approach, the final risk was 1.1 × 10−5, which was almost 24 times higher compared with the current method. The contribution of nanoparticles to the risk value grew from barely 6% to an alarming 88%. Therefore, the enhanced method can lead to more realistic results when assessing the health risks of nanoparticles.

19.
ACS Omega ; 6(42): 28098-28118, 2021 Oct 26.
Article in English | MEDLINE | ID: mdl-34723009

ABSTRACT

The development of flexible, lightweight, and thin high-performance electromagnetic interference shielding materials is urgently needed for the protection of humans, the environment, and electronic devices against electromagnetic radiation. To achieve this, the spinel ferrite nanoparticles CoFe2O4 (CZ1), Co0.67Zn0.33Fe2O4 (CZ2), and Co0.33Zn0.67Fe2O4 (CZ3) were prepared by the sonochemical synthesis method. Further, these prepared spinel ferrite nanoparticles and reduced graphene oxide (rGO) were embedded in a thermoplastic polyurethane (TPU) matrix. The maximum electromagnetic interference (EMI) total shielding effectiveness (SET) values in the frequency range 8.2-12.4 GHz of these nanocomposites with a thickness of only 0.8 mm were 48.3, 61.8, and 67.8 dB for CZ1-rGO-TPU, CZ2-rGO-TPU, and CZ3-rGO-TPU, respectively. The high-performance electromagnetic interference shielding characteristics of the CZ3-rGO-TPU nanocomposite stem from dipole and interfacial polarization, conduction loss, multiple scattering, eddy current effect, natural resonance, high attenuation constant, and impedance matching. The optimized CZ3-rGO-TPU nanocomposite can be a potential candidate as a lightweight, flexible, thin, and high-performance electromagnetic interference shielding material.

20.
Langmuir ; 37(28): 8557-8568, 2021 Jul 20.
Article in English | MEDLINE | ID: mdl-34233120

ABSTRACT

Here, we present an integrated approach to the weakly viscoelastic fluid printability assessment by using global dimensionless criteria (DC). The problem was studied on a model semidiluted polyvinylpyrrolidone water-based ink. For the study purpose, the ink composition was kept as simple as possible. First, the solution density, viscosity, and surface tension were determined. Obtained data were used for testing limitations of DC printability diagrams already available for Newtonian fluids. A replotted version of the original Kim and Baek's map was developed emphasizing the importance of surface tension in the drop formation process. Another set of DC (e.g., Ec and De) was also used for a real evaluation of the viscoelasticity effect on both jetting conditions and drop formation. The polymer relaxation time as a crucial parameter for viscoelasticity was shown to be calculated using the Kuhn segment length rather than from Zimm and Rouse theories for diluted polymer systems. Then, a two-dimensional diagram using four DC (Oh and De with Ec and El as parameters) is proposed based on the famous McKinley's work. The diagram describes the interplay of possible forces responsible for filament thinning and breakup processes. Obtained results were supported by further experiments involving drop ejection and formation, determination of critical polymer concentration, and others. The proposed diagram promises a useful initial step in further investigations of viscoelasticity of polymer compounds by inkjet printing.

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